Here lies the burning question - what is within limits.
At this stage we still don't know what a/c type is involved and therefore we don't know the 'limits'. Until then we can only 'assume' that 'no ice is good ice'. hence I advocate that the cabin crew were quite within their rights to express their concern and if said F/O chose to argue about it rather than give a rational explanation regarding limits or admit that de-icing was required then that is probably why the case has come to a head.
Suppose you could say he is skating on thin ice (I'll get my coat!!)
Rgds
CL747